Oil-soluble metal sulfonates and lubricants containing them



United States Patent 3,367,865 GIL-SULUBLE METAL fiULFONATES AND LUBRICANTS CONTAINING THEM David A. Gudelis, Sarnia, Ontario, Canada, assignor to Esso Research and Engineering Company, a corporation of Delaware N0 Drawing. Continuation-impart of application Ser. No. 111,387, May 19, 1961. This application Nov. 25, 1966, Ser. No. 596,819

7 Claims. (Cl. 25233) This application is a continuation-impart of application Ser. No. 111,387, filed May 19, 1961.

The present invention concerns improvements in oilsoluble metal salts of hydrocarbon sulfonic acids, said salts being used as detergents and dispersants in lubricating oils and particularly in mineral lubricating oils. The invention also concerns an improved process for preparing alkaline earth metal hydrocarbon sulfonates and improved hydrocarbon compositions containing the said sulfonate salts.

It is known to employ alkaline earth metal sulfonates as additives for lubricants, especially those designed for heavy duty service in internal combustion engines. Lubricating oils containing alkaline earth metal sulfonates have an improved detergent action on the parts of the engines that they lubricate and are capable of being used under severe conditions of load and temperature where they prevent the sticking of rings and pistons which would otherwise result from the formation of varnish.

The metal salts of sulfonic acids that have been used in the prior art as detergent additives for lubricants are of two types; namely, salts of petroleum sulfonic acids and salts of synthetic sulfonic acids. Petroleum sulfonates that are generally used in lubricating and other oil compositions are derived from high molecular weight sulfonic acids, the latter being produced by the treatment of petroleum oils of the lubricating oil range with fuming sulfuric acid. These sulfonic acids generally have molecular Weights of about 300 to 1200, although salts of sulfonic acids having higher molecular weights, e.g. 2000, are also useful in some applications. More generally the sulfonic acids whose metal salts are employed in crankcase lubricants have molecular weights in the range of about 400 to 800. Synthetic sulfonates are derived from relatively pure alkyl aryl sulfonic acids having usually more than 10 carbon atoms per molecule. For example, sulfonated products of alkylated aromatics such as benzene, toluene, xylene, and naphthalene, alkylated with olefins or olefin polymers of the type of polypropylene, polyisobutylene, etc., can be used. Calcium sulfonates are generally preferred for lubricating compositions because of their lower ash content. Calcium sulfonates will generally contain about 2 to 5 wt. percent calcium, Whereas barium sulfonates will generally contain about to Wt. percent barium.

It has now been found that an alkaline earth sulfonate having superior detergent and varnish preventing prop erties can be prepared by a novel process wherein benzene is alkylated With a particular type of dimerized olefin and then sulfonated and converted to the metal salt in the usual manner. In accordance with this invention, a

5 to C olefin fraction is dimerized by contacting the said fraction with a silica-alumina catalyst, after which a high boiling fraction of the resulting dimer, having an initial boiling point of 500 F, is used to alkylate benzene to provide a heavy alkylate having an initial boiling point of about 640 F. The latter heavy alkylate is then sulfonated and the resulting sulfonic acids are converted to alkaline earth metal salts. The salts thus prepared have been found to be superior in heavy duty engine performance to similar alkaline earth metal salts of the same molecular Weight prepared from sulfonated detergent alkylate bottoms.

In copending application Ser. No. 111,387, of which the present application is a continuation-in-part, it is disclosed that C to C monoolefins can be selectively dimerized and/or codimerized to C to C monoolefins in the presence of a silica-alumina catalyst, and that improved household detergents can be prepared by alkylating benzene with selected fractions of the dimer and/ or codimer olefins, so prepared, sulfonating and neutralizing to obtain alkyl benzene sulfonate detergents. One preferred embodiment of that invention relates to dimerizing a C to C olefin, obtained as a byproduct in the commercial preparation of tetrapropylene for tetrapropylbenzene detergents. This commercial preparation of tetrapropylene is usually done by reacting propylene in the presence of a phosphoric acid catalyst which is conveniently referred to as UOP catalyst. The phosphoric acid is usually supported on kieselguhr. In that embodiment of the invention it was discovered that in addition to selectively obtaining higher molecular weight olefins, i.e. C to C olefins, than are obtained from phosphoric acid polymerization (desirable since the detergents prepared from these olefins have superior washing properties to those prepared from lower molecular Weight olefins) these olefins have a low cyclic olefin index.

While it is not intended to limit the invention by any theory it is postulated that in the inventive process the active sites on the catalyst are so spaced with relation to the length of the chain of the feed olefin that growth type polymerization is obtained. This dimerization may be represented, for example, by the following equation:

(or double bond in this position) (The dashed or dotted lines merely indicate carbon positions.) It is further postulated that the dimerized olefin has an internal double bond, which is stabilized by the methyl group, so that on alkylation only specific alkylate isomers are obtained. Thus, on alkylation the phenyl group will be attached on carbons l, 2, or 3, preferably 3 when the double bond joins carbons l and 2, producing alkyl benzene sulfonate detergents which are biodegradable.

The feed stock for the production of dimerized olefins for superior higher molecular weight detergents in accordance with the present invention Will be the low boiling polymer from a conventional phosphoric-acid-on-kieselguhr polymerization process. Preferably C to C olefins are supplied to the process of the present invention. Particularly useful are a C to 400 F. cut, predominantly C olefins, and a 360 to 400 F. cut, predominantly C olefins. Although C to 500 F. olefins can also be used. It is noted that these byproduct materials from the conventional process are of little value other than as fuels, etc. and that recycle of these materials in the conventional phosphoric-acid-on-kieselguhr process does not appreciably increase the yield of the C and higher materials.

The silica-alumina catalysts which can be used in the present process contain a ratio of silica to alumina of 1:1 to 15:1 and preferably contain from 50 to silica and from 50 to 10% alumina. In addition, small amounts, i.e. not more than 10%, of other metal oxides such as iron and nickel may be present but are only coincidental in the success of the present process. These catalysts may be prepared by methods well known in the art, such as by impregnating silica with alumina salts, by directly combining precipitated hydrated alumina and silica or by joint precipitation of alumina and silica from aqueous solutions of these salts. Following this initial step in its preparation, the catalyst is washed and dried and then heated to activate it. This latter heating step ensures that the desired structure and acidity of the catalyst will be obtained for optimum activity and selectivity in the process. Thus, the catalyst is heated at temperatures in the range of 300 to 1500 F., preferably 900 to 1100 F., e.g. 1000 F., preferabl with hot air for times in the range of /2 to 25 hours, preferably 1 to 3 hours, e.g. 2 hours. Surface areas of above 350M 2/g., e.g. 500M 2/ g. are obtained. It should be noted that these catalysts do not include the molecular sieve type catalysts.

The catalysts may be used either in the form of pellets for fixed or moving bed processes or in the form of powder for fluidized operations. Where the catalyst is used in the form of pellets, these catalysts may be prepared by pelleting to form preferably /s" to /2 pellets, e.g. pellets, followed by heating as previously described to activate the catalyst.

The silica-alumina catalysts used in thi invention are preferably fresh catalysts but in addition may less preferably be spent or equilibrium cracking catalysts which have been used in the cracking of hydrocarbons, e.g. gas oils, to produce lower boiling materials. Such cracking operations are commercially conducted, e.g. at temperatures of 800 to 1200 F., e.g. 1070 F., and pressures of 10 to 500 p.s.i.g, e.g. 200 p.s.i.g. In these processes activity of the catalyst progressively decreases due to the accumulation of coke and other materials thereon. Such catalysts are ordinarily continuously regenerated in the process by burning off the deposited coke at temperatures usually of less than about 1150 F., e.g. 950 F., in a stream of air which may be diluted with an inert gas in order to control the rate of burning. Regeneration processes, however, do not completely restore the catalyst to its original activity, so that regeneration becomes progressively less effective. This results in part from the deposition of foreign materials, principally metals or metal compounds, on the catalyst which are not removed in the regeneration process. Additionally, the surface area of the catalyst progressively decreases. When the cracking activity after regeneration has decreased from 70 to 50% of its original activity, regeneration thereof is no longer feasible and the catalyst is referred to as spent catalyst and is discarded. Such catalysts ordinarily have surface areas of about 100M 2/ g., which surface areas are, of course, far below optimum for the present process. Catalysts having an activity of above 50 to 70% of original activity are referred to as equilibrium catalysts and these catalysts may be used in the process (although of course surface area for these catalysts also will be low). A typical spent catalyst containing 87% SiO and 13% Al O when fresh may contain, when spent, 1 to iron and 0 to 1% nickel as impurities. In this invention, however, the amount and nature of the metallic impurities are of little consequence.

According to the present invention, reaction conditions in the dimerization and/ or codimerization should include temperatures in the range of 200 to 500 F., preferably 350 to 450 F., e.g. 400 F., pressures of 200 to 2000 p.s.i.g., preferably 500 to 1000 p.s.i.g., e.g. 800 p.s.i.g., space velocities of 0.05 to 0.80 g.p.h./lb. of catalyst, preferably 0.08 to 0.50 g.p.h./lb. of catalyst, e.g. 0.12 or 0.20 g.p.h./lb. of catalyst. In a preferred embodiment the feed contains less than 0.01 mol percent water, preferably less than 0.007 mol percent water, e.g. 0.004 mol percent water. This may be obtained if necessary by drying the feed and/or catalyst after regeneration. The catalyst will ordinarily be regenerated after a catalyst life of about 50 to 100 gallons of net polymer/lb. of

catalyst, preferably about '60 to 80 gallons of net polymer/lb. of catalyst, e.g. gallons of net polymer/lb. of catalyst. This regeneration i conducted at temperatures in the range of 800 to 1500 F., preferably 900 to 1200 F., e.g. 1000 F. for contacting times of 2 to 20 hours, preferabl 5 to 10 hours, e.g. 8 hours. Shorter times are, of course, used with the higher temperatures. This contacting is preferably conducted in the presence of an inert gas and, if it is desired to burn off carbon, also in the presence of air. The temperatures described above are desirable in order to obtain the preferred structure of the catalyst following regeneration.

Alkylation is carried out utilizing benzene in the presence of a Friedel-Crafts type catalyst at temperatures in the range of 15 to 160 F., e.g. 40 F. for times of 5 to 60 minutes, e.g. 18 minutes. Suitable catalysts include, for example, AlCl HF, BF and AlBr polyphosphoric acid, H and aluminum chloride hydrocarbon complexes. Aluminum chloride is the preferred catalyst, which may be either fresh AlCl or spent AlCl sludge from a previous alkylation step, fortified by the addition of 5 to 20 Wt. percent of fresh AlCl The feed olefin for the alkylation reaction is obtained by fractionation from the product of dimerization and/ or codimerization. This feed for the present invention is preferably the fraction having an initial boiling point of about 500 F., i.e. all of the product that boils above 500 F, the upper boiling point not being critical.

It is generally desirable to maintain in the reaction mixture a volume ratio of aromatic hydrocarbon to olefin of at least 3:1, e.g. 5:1, although ratios up to 20:1 may be used.

Although temperatures during alkylation with AlCl can range as high as 140 F., it is preferred to use temperatures of between 20 and 80 F., e.g. 40 or 50 F. Weight ratios of olefin to catalyst will be in the range of about 30:1 to 7:1, e.g. 20:1 or 10:1. Additionally, in the case of the use of aluminum chloride, an activator such as HCl can be added in an amount of from 15 to 40 wt. percent, e.g. 20 wt. percent, based on aluminum chloride.

If a liquid hydrogen fluoride catalyst is used for alkylation, it is preferred to use an acid-to-hydrocarbon reactants volume ratio of 0.1:1 to 1.021, e.g. 0.311 and temperatures in the range of 30 to 60 F., e.g. 50 F. The concentration of this catalyst can range from to 100% HP by weight, its water content being maintained very low, e.g. no higher than 1 or 2% by weight, the remainder being dissolved hydrocarbon material.

The alkylated aromatic fraction is recovered from the alkylation reaction mass and is sulfonated in known manner, e.g. by contact with an excess of concentrated sulfuric acid, oleum, ClSOgH, sulfur trioxide, etc. Preferably, for the production of satisfactory oil-soluble metal sulfonates for the present invention the alkylate fraction having an initial boiling point of about 640 to 650 F. is sulfonated. A typical alkylate having a boiling range of 650 F.+ has an initial boiling point of 603 F., 5 liquid percent off at 658 F, 10% off at 670 F, 30% off at 694 F., 50% off at 722 F, 70% off at 755 F., off at 830 F., off at 870 F., and final boiling point above 990 F. The sulfonation can be carried out at temperatures up to 140 F., preferably for oleum 60 to 140 F., e.g. 120 F. The acid concentration is preferably at least 97%. Acid up to concentration and preferably oleum containing up to e.g. 20 wt. percent S0 or higher, can be employed. With higher acid concentration, lower reaction times are required, e.g. about 3 to 4 hours with 98% acid, about 2 hours with 100% acid, and preferably 0.5 to 1 hour, e.g. 0.7 hour, with oleum. Volume ratios of sulfuric acid to hydrocarbon can range from 0.8:1 to 1.25:1, a 1:1 ratio being suitable.

The sulfonation product mixture can be separated by layering to remove part of the excess spent acid before neutralizing or it can be neutralized directly. When neutralized the sulfonic acids are thus converted to sulfonic acid salts and the excess sulfuric acid into sulfate. The sulfate normally settles out, and its complete removal is effected by filtration. If necessary, any sludge that forms during sulfonation that cannot be removed by simple settling can be removed by treating the product with a filter aid such as diatomaceous earth. Also, if it is found necessary, the sulfonic acids can be blown with nitrogen to remove S To prepare the alkaline earth metal salts, the sulfonic acids can be neutralized directly with an alkaline earth metal base such as BaCO Na CO Ca(OH) etc., although more usually the sodium or other alkali metal salt is first formed, followed by conversion to alkaline earth metal salt by double decomposition. The neutralization is generally carried out by contact with basic aqueous solution at temperatures of from 65 to 160 F., those between 80 and 125 F., e.g. 100 F., being preferred.

Conversion of alkali metal salts to alkaline earth metal salts by double decomposition can be accomplished by reacting the alkali metal sulfonate with an alkaline earth metal salt, such as the chloride, using any of the standard procedures known to those skilled in the art.

Double decomposition of the alkali metal sulfonates with aqueous solutions of salts of the desired alkaline earth metal can conveniently be carried out using an aqueous alcohol solution of the sulfonate. Thus, for example, a 10 to 30% aqueous solution of an alkaline earth metal salt, in an amount 10 to 200% in excess of the theoretical amount required, is well mixed with the alkali metal sulfonate solution at substantially atmospheric temperature. The alkaline earth sul'fonate, containing some alkali metal sulfonate, salts, and water, precipitates as a curdy mass. This mass can be fluxed with lubricating oil, dehydrated by heating to 275 to 325 F. and filtered free of insoluble material. Alternatively, the alkali metal sulfonate solution and a 10 to 30% aqueous solution of alkaline earth metal salt in 10 to 200% excess of theoretical can be emulsified with the oil in which the sulfonate will be dissolved to form the desired sulfonate concentrate. In some cases a small amount of the alkaline earth hydroxide can also be incorporated to maintain alkalinity. The mixture is then heated to 275 to 325 F. to drive off the water and the product filtered to remove insoluble salts.

Still another alternate method is to dissolve the sodium sulfonate in a mineral oil base in a concentration equivalent to that desired for the alkaline earth metal sulfonate and then emulsify the oil solution with an aqueous solution of an alkaline earth metal inorganic salt such as calcium chloride. As in the other double decomposition methods, an excess of the inorganic acid salt is used and the double decomposition is effected at a temperature of about 100 to 200 F. The reaction takes place rapidly, and the emulsion can then be permitted to settle. The separated oil layer can then be heated to 300 F. or higher to etfect dehydration, after which the oil solution of the alkaline earth metal sulfonate can be filtered.

Concentrates prepared in accordance with this invention will comprise a mineral lubricating oil to which has been added from 10 to 80 wt. percent, or more usually from about 30 to 60 wt. percent, of the alkaline earth metal sulfonate.

The alkaline earth metal sulfonates prepared in accordance with this invention can be added to lubricating compositions in concentrations ranging from about 0.1 to about 10 wt. percent, or more usually in concentrations of from about 0.4 to about 5 wt. percent. The lubricating oils include not only mineral lubricating oils but also synthetic oils including synthetic hydrocarbons, dibasic acid esters, such as di-Z-ethyl hexyl sebacate, carbonate esters, phosphate esters, polysilicones, polyglycols, and the like. The lubricant compositions may also contain other additives such as dyes, pour point depressants, e.g. Wax alkylated naphthalene, antiwear agents such as zinc dialkyl dithiophosphates, antioxidants such as phenyl alpha EXAMPLE 1 Part A-Preparation of olefin: dimer Using as the feed stock a light polymer fraction having C olefins and higher up to a final boiling point of 400 F., said polymer having been obtained by polymerizing propylene with UOP catalyst (phosphoric acid on kieselguhr), several runs were made in which the feed was contacted with silica-alumina catalyst at temperatures ranging from 360 to 400 F. and pressures of from 500 to 2000 p.s.i.g. The conditions of each run and the product distribution of the dimer thereby obtained are given in Table I.

TABLE I.-DIMERIZATION OF UOP LIGHT POLYMER OVE R SILIGA-ALUMINA CATALYST Catalyst: 12% Alma-88% S102 Feed: Propylene UOP light polymer, boiling C5400F.

Run No 1 2 3 4 5 6 Temp, F 400 400 400 360 400 360 Pressure, p.s.i.g. 800 800 800 1500 500 500 Space Velocity, g.p.h./lb 0. 12 0. 25 0. 37 0. 12 0. 12 0. 12 Product Distribution, Liquid Vol.

Percent:

(la-400 11- 45 52 62 47 52 56 400500 F 12 11 11 10 11 10 500 F.+ 43 37 27 43 37 34 Part B-Preparation of alkylate An olefin fraction having an initial boiling point of 500 F. and prepared in the manner of Run 5 of Example 1 was used to alkylate benzene with fresh aluminum chloride catalyst in the presence of HCl to maintain catalyst activity. The extent of reaction was followed by measuring bromine numbers and running the reaction until the bromine number was below 0.5. The reaction conditions and the product yields are given in Table II.

TABLE II.ALKYLATION OF BENZENE WITH HEAVY OLEFINS Run A:

Benzene/olefin, volume 4/1 Temperature, F 50 AlCl wt. percent on olefin 8 Product yield, L.V. percent on olefin:

Light alkylate, 200 to 650 F 32 Heavy alkylate, 650 F.+ 73

Total 105 EXAMPLE 2 Part APreparati0n of dimer of UOP tetrapropylene Using as feed stock a 360-400 F. UOP polymer fraction, said polymer having been obtained by polymerizing propylene with UOP catalyst, several runs were made in which the feed was contacted with the silica-alumina catalyst used in Example 1. The conditions of each run and product composition are shown in Table III.

TABLE III.DIMERIZATION OF UOP TETRAPROPYLENE FRACTION OVER SILICA-ALUMINA CATALYST Run No 7 8 9 Temperature, F 400 400 400 Pressure, p.s.i.g 200 800 1, 500 Space velocity, v./v./l1r 1 1 1 Product Distribution, Vol. Percent:

Unconverted feed-.... '70 58 54 400-500" F. fraction. 10 10 10 500 F.+Fraction....- 20 32 36 Part B EXAMPLE 4 Part A-Preparation of alkylate Using in one case a dimer of a predominantly C olefin prepared as described in Example 1, Run No. 5, and in a second case a dimer of essentially C olefins obtained as described in Example 3, Run No. 8, and taking in each case the entire fraction boiling above 500 F., benzene was alkylated with each fraction using aluminum chloride catalyst. The alkylation conditions were 4/1 benzene toolefin ratio, 5080 F. temperature and 8 wt. percent AlCl on olefin. The characteristics of the heavy alkylate thereby obtained in each case are given in Table V, along with the characteristics of a heavy alkylate identified as detergent alkylate bottoms, these bottoms being the fraction boiling at 650 F. and higher obtained as a byproduct in making detergent alkylate by alkylating benzene with tetrapropylene obtained by polymerizing propylene with phosphoric acid catalyst.

TABLE V.HEAVY ALKYLATE QUALITY Aniline point, F

Distribution of side chain by mass spectromster, rnol percent:

Avg. carbon number of tot Avg. molecular weight TABLE IV.ALKYLATION OF HEAVY OLEFINS [Olefin Iced source: UOP tetrapropylene dimer, 500 EK] Run B C D Alkylation conditions:

Temperature, F 9 0 9 0 50 Benzene/olefin volume ratio- 4/1 4/1 4/1 A101 wt. percent on olefin 7.1 6. 9 6. 4 Total alkylate distribution, L.V. percent:

EXAMPLE 3 A portion of the olefin dimer prepared as in Run 4, Example 1 is used to alkylate benzene in the presence of an AlCl -HCl catalyst. Alkylation conditions are:

AlCl addition rate -wt. percent on olefin 8 HCl addition rate --wt. percent on AlCl 20 Benzene/olefin volume ratio 4:1 Reactor temperature F 50 The alkylates obtained are sulfonated with 20% oleum at 60 to 140 F. by adding the oleum to the alkylate. The weight ratio of oleum to hydrocarbon is 1.4:1 and the materials are reacted for 45 minutes. Following reaction, the sulfonation product mixture is neutralized to a pH of 7 with aqueous sodium hydroxide to obtain the sodium salts of the sulfonic acids admixed with sulfates produced from excess spent sulfuric acid. The neutralization is carried out at a temperature of about 115 F. utilizing a reaction time of about 15 minutes. The sodium salts are converted to calcium salts by double decomposition with calcium chloride.

It will be seen from the information in Table V that the average molecular weight, the average carbon number of the total alkylate, and the distribution of side chains in products made in accordance with the present invention are quite similar to those of a typical detergent alkylate bottoms.

Part BPreparati0rz of sulfonate Each of the alkylates that was prepared as described in Part A of this example was sulfonated with S0 in the following manner. The alkylate was mixed with an equal volume of hexane and then while the mixture was heated under reflux at about F., S0 in a nitrogen carrier stream (5% S0 was bubbled through the hexanealkylate mixture until a total mol ratio of S0 to alkylate of 1.1 to 1 was attained. The rate of S0 addition was in the range of 0.08 to 0.14 gram of S0 per gram of alkylate per hour. At the end of the sulfonation treat, the hexane was stripped off by bubbling nitrogen through the mixture at 125 F. over a period of about two hours. The sulfonic acid mixture thereby obtained was then converted to sodium salts by pouring the mixture into a 10% solution of sodium hydroxide in a mixture of 30% ethanol and 70% water, the amount of sodium hydroxide being slightly more than the calculated amount needed to neutralize the sulfonic acids. Neutralization temperature was about F. In each case it was found that about 7 wt. percent of unsulfonated hydrocarbon was present.

The sodium sulfonates thus formed were mixed with a light mineral lubricating oil in a proportion calculated to give about a 45% concentrate of the ultimate calcium sulfonate in oil, after which the water and alcohol were driven off by heating. Then in each case the oil solution of sodium sulfonate was emulsified with a saturated solution of calcium chloride, the amount of calcium chloride used being about 2.5 to 3 equivalents of calcium per equivalent of sodium. The emulsion was formed by stirring the mixture at 190 to 200 F. Reaction tool; place within 15 to 20 minutes. The emulsion was then allowed to settle and the aqueous layer was drawn oii, after which a small amount of slaked lime, i.e., Ca(OH) was added with stirring at ambient temperatures. The amount of lime was about 0.5 equivalent per equivalent of calcium sulfonate. The mixture was then heated to 300 F. to drive off water and the resulting calcium sulfonate concentrate in oil was filtered through diatomaceous earth. The coneentrate contained about 45 wt. percent of the calcium sulfonate.

EXAMPLE 5 Testing of oil blends Comparative oil blends were prepared to evaluate the sulfonates of the present invention as dispersant components in a balanced blend of dispersant components and alkalinity-contributing components in an oil composition designed for severe service in a diesel engine. Each blend was prepared by simple mixing of 14 vol. percent of an additive concentrate blend with 86 vol. percent of a re-- fined, high viscosity index parafiinic lubricating oil of SAE 30 viscosity grade. The additive concentrate blend was prepared by simple mixing of four additives, each of which was in turn a concentrate in mineral lubricating oil. The concentrate blend consisted of 16 vol. percent of mixed barium-calcium nonyl phenol sulfide concentrate (35 Wt. percent in oil), 9 vol. percent of barium nonyl phenate concentrate (50 wt. percent in oil), 5 vol. percent of an oil concentrate of a 300 base number calcium synthetic hydrocarbon sulionate (28 wt. percent sulfonate, 24 Wt. percent CaCO in oil), and 70 vol. percent of the sulfonate concentrate being evaluated in the test (45 wt. percent in oil). The purpose of the metal phenol sulfide was to impart an inhibitor function to the oil, while the overbased sulfonate and the metal phenate ensured that the oil would have sufiicient reserve alkalinity. It is to be noted that of the total sulfonate in the blend for each 96 parts of the sulfonate being evaluated there were only about 4 parts of the alkalinity-contributing sulfonate.

Each of the comparative blends thus prepared was subjected to the 240-hour Caterpillar 1-G Test, which is a test that is used to certify military Series 3 lubricants for the Caterpillar diesel engine. This test is fully described in the Caterpillar Test Manual. At the end of each test the engine is dismantled and inspected for deposits. The most significant rating is that of the engine piston. A merit rating is used in which a value of 100 signifies a perfectly clean piston, and a value of 0 signifies a completely dirty piston. The results obtained in these tests are given in the following Table Vi. A comparative test was run with the calcium salt of the sulfonated product of the detergent alkylate bottoms referred to in Table V.

TABLE VI.-CATERPILLAR ENGINE TEST DAT/b- 1 BestzlOO.

It will be noted that in the Caterpillar Engine Test each of the calcium sulfonates prepared in accordance with the present invention gave a much cleaner piston than did the prior 'art calcium salt of sulfonated detergent allrylate bottoms.

It is not intended that the scope of this invention be limited by the specific illustrations thereof appearing in the examples.

What is claimed is:

1. An improved process for preparing an oil-soluble alkaline earth metal hydrocarbon sulfonate which comprises the steps of dimerizing a monoolefin fraction in the C to C range by contacting said fraction with an activated silica-alumina catalyst having a silica-to-alumina weight ratio of from 1:1 to 15:1, said contacting being conducted at a temperature in the range of 200 to 500 F. at a pressure of 200 to 2000 p.s.i.g. and a feed rate of 0.05 to 0.80 g.p.h./lb. of catalyst, fractionating the dimer product to obtain a high boiling fraction boiling above 500 F., alkylating benzene with said high boiling dimer fraction in the presence of a Friedel-Crafts catalyst, thereafter segregating from the resulting alkyl benzene a heavy alkylate fraction having an initial boiling point of at least 640 F., subjecting said heavy alkylate fraction to sulfonation and converting the sulfonated product to an alkaline earth metal salt.

2. Process as defined by claim 1 wherein the said olefin fraction is predominatnly a tripropylene fraction obtained by polymerizing propylene in the presence of a catalyst comprising phosphoric acid on kieselguhr.

3. Process as defined by claim 1 wherein the said olefin fraction is predominatnly a tetr'apropylene fraction obtained by polymerizing propylene in the presence of a catalyst comprising phosphoric acid on kieselguhr.

d. An alkaline earth metal sulfonate prepared by the process defined by claim 1.

5. A calcium sulfonate prepared by the process defined by claim 1.

6. A lubricating oil composition comprising a major proportion of a mineral lubricating oil and from 0.1 to 10 Wt. percent of alkaline earth metal sulfonate prepared by the process defined by claim 1.

7. A concentrate comprising a mineral lubricating oil to which has been added from about 10 to about wt. percent of an alkaline earth metal sulfonate prepared by the process defined by claim 1.

References Cited UNITED STATES PATENTS 2,622,113 12/1952 Hervert 260-683.15 2,807,590 9/1957 McDonald et al. 25233 XR 2,880,173 3/1959 Honeycutt 252-33 2,886,609 5/1959 Halaka 260-671 3,009,972 11/1961 Johnson 260-683.15

DANIEL E. WYMAN, Primary Examiner. 

1. AN IMPROVED PROCESS FOR PREPARING AN OIL-SOLUBLE ALKALINE EARTH METAL HYDROCARBON SULFONATE WHICH COMPRISES THE STEPS OF DIMERIZING A MONOOLEFIN FRACTION IN THE C5 TO C15 RANGE BY CONTACTING SAID FRACTION WITH AN ACTIVATED SILICA-ALUMINA CATALYST HAVING A SILICA-TO-ALUMINA WEIGHT RATIO OF FROM 1:1 TO 15:1, SAID CONTACTING BEING CONDUCTED AT A TEMPERATURE IN THE RANGE OF 200 TO 500*F. AT A PRESSURE OF 200 TO 2000 P.S.I.G. AND A FEED RATE OF 0.05 TO 0.80 G.P.H./LB. OF CATALYST, FRACTIONATING THE DIMER PRODUCT TO OBTAIN A HIGH BOILING FRACTION BOILING ABOVE 500*F., ALKYLATING BENZENE WITH SAID HIGH BOILING DIMER FRACTION IN THE PRESENCE OF A FRIEDEL-CRAFTS CATALYST, THERAFTER SEGREGATING FROM THE RESULTING ALKYL BENZENE A HEAVY ALKYLATE FRACTION HAVING AN INITIAL BOILING POINT OF AT LEAST 640*F., SUBJECTING SAID HEAVY ALKYLATE FRACTION TO SULFONATION AND CONVERTING THE SULFONATED PRODUCT TO AN ALKALINE EARTH METAL SALT.
 6. A LUBRICATING OIL COMPOSITION COMPRISING A MAJOR PROPORTION OF A MINERAL LUBRICATING OIL AND FROM 0.1 TO 10 WT. PERCENT OF ALKALINE EARTH METAL SULFONATE PREPARED BY THE PROCESS DEFINED BY CLAIM
 1. 